Effect of poling process on piezoelectric properties of sol-gel derived BZT-BCT ceramics

Lead free piezoelectric ceramics barium zirconate titanate-barium calcium titanate, [xBZT-(1−x)BCT] (0.48 ≤ x ≤ 0.52), were synthesized by sol-gel method. Calcination of the as-synthesized precursor powders resulted in crystalline powders with single-phase perovskite structure at 700 °C, which is significantly lower than that obtained by solid-state reaction. Solid-state sintering at 1450 °C resulted in highly dense microstructure with ≥95% of the theoretical density. The effect of electric poling on the piezoelectric properties of the sintered [xBZT-(1−x)BCT] ceramics is studied with varying poling temperatures and poling fields. The results indicated that optimized poling conditions are required in enhancing the piezoelectric properties of [xBZT-(1−x)BCT] ceramics. The morphotropic phase boundary (MPB) composition, 0.5BZT-0.5BCT, showed a high remanent polarization (Pr) of 12.2 μC/cm2 and a low coercive field (Ec) of ∼0.14 kV/mm. The optimized poling conditions resulted in high piezoelectric charge coefficient d33 ∼ 637 pC/N, large electromechanical coupling coefficient kp ∼ 59.6%, a large strain of 0.157%, a large piezoelectric voltage constant g33 ∼ 29 mV m/N for (0.5BZT-0.5BCT) composition. In this report, the excellent piezoelectric properties of the sol-gel derived BZT-BCT ceramics has been analysed and correlated to its structure and poling conditions.